Online Image Add Noise Tool

What this tool actually does

Single-image noise tool. Noise amount and Noise strength are distinct controls, each 0-100%, step 0.01. Default amount 30%, default strength 35%.

Checkable behavior

Monochrome (grayscale noise) checkbox is on by default. It applies the same random offset to red, green and blue; switching it off draws independent offsets per channel. It does not convert the entire source image to grayscale.

Controls, output and limitations

For each pixel, selection is Math.random()*100 < amount. For selected pixels, offset is (Math.random()-0.5)*255*strength/100. Channel output is clamped to the valid range. Amount zero always leaves pixels unchanged.

Worked example: use a solid mid-gray image, amount 30%, strength 20%, monochrome on. Roughly 30% of pixels are selected, not an exact count. Selected RGB channels receive the same random offset in [-25.5,25.5). Expect irregular light/dark grain while other pixels remain unchanged.

Strength 0 produces no channel offset. At amount 100 every pixel is selected. Increasing amount changes grain coverage; increasing strength changes variation magnitude.

Math.random has no user seed control here. Re-running with identical settings does not guarantee the same pixel pattern. Identical settings can produce different random grain patterns.

The source image is processed locally in the browser and a preview/download is provided. Use the displayed upload guidance and inspect the exported image before publishing.